1. Field of the Invention
This invention relates to metal air cells, and particularly to a metal air cell incorporating an air flow system.
2. Description of the Prior Art
Electrochemical power sources are devices through which electric energy can be produced by means of electrochemical reactions. These devices include metal air electrochemical cells such as zinc air and aluminum air batteries. The anode is generally formed of oxidizable metals, which in some instances, may be replaced or recharged. The cathode generally comprises an air diffusion electrode for oxidizing air. The electrolyte is usually a caustic liquid that is ionic conducting but not electrically conducting.
Metal air electrochemical cells have numerous advantages over traditional hydrogen-based fuel cells. Metal air electrochemical cells have high energy density (W*hr/Liter) and high specific energy (W*hr/kg). Further, the supply of energy provided from metal air electrochemical cells is virtually inexhaustible because the fuel, such as zinc, is plentiful and can exist either as the metal or its oxide. Additionally, metal air cells are capable of operating at ambient temperatures. Moreover, solar, hydroelectric, or other forms of energy can be used to convert the metal from its oxide product back to the metallic fuel form. Unlike conventional hydrogen-oxygen fuel cells that require refilling, the fuel of metal air electrochemical cells is recoverable by electrically recharging. The fuel may be solid state, therefore, safe and easy to handle and store. In contrast to hydrogen-oxygen fuel cells, which use methane, natural gas, or liquefied natural gas to provide as source of hydrogen, and emit polluting gases, the metal air electrochemical cells results in zero emission.
The metal air electrochemical operate at ambient temperature, whereas hydrogen-oxygen fuel cells typically operate at temperatures in the range of 150xc2x0 C. to 1000xc2x0 C. Metal air electrochemical cells are capable of delivering higher output voltages (1.5-3 Volts) than conventional fuel cells ( less than 0.8V). Due to these advantages, metal air electrochemical cells can be used as power sources of all kind of applications, such as stationary or mobile power plant, electric vehicle or portable electronic device, etc.
One of the principle obstacles of metal air electrochemical cells is control of the temperature of the electrochemical cell. The electrochemical reaction in the cell increases temperature, primarily from internal resistance. With conventional metal air systems, ambient temperature increases in combination with the internal resistance detrimentally affect cell performance. Further, ambient temperature decreases generally results in lower conductivity of the electrolyte, thus detrimentally affecting cell output.
Therefore, a need remains in the art for a metal air cell that minimizes or preferably eliminates problems associated with temperature variations.
The above-discussed and other problems and deficiencies of the prior art are overcome or alleviated by the metal air cell of the present invention, wherein a frame for supporting the cathode and the anode is configured with a periphery air flow path channel for storing heat generated by air that has reacted with the cathode oxidant side, and a reaction path region complementary to the cathode oxidant side.
A method of operating an electrochemical cell is also provided including:
directing unreacted oxidant substantially directly to the cathode and directing reacted oxidant out of the cell in a first mode of operation; and
directing unreacted oxidant substantially directly to the cathode and directing reacted oxidant into a periphery region to retain heat in a second mode of operation.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.